Flash spinning of polyethylene to form non-woven sheets is known in the art: see, for example, Brethauer et al., U.S. Pat. No. 3,851,023.
U.S. Pat. No. 4,086,204 discloses the use of Chimassorb 994 as a stabilizer for polyethylene.
Flash spun polyethylene nonwoven fibrous sheets containing an ultra-violet stabilizer are commercial products. The ultra-violet stabilizer is a necessary component of the product in that it protects both the nonwoven sheet from UV degradation, and other components, such as antioxidents, from UV degradation. Most of the commercial flash spun products are made by spinning the polyethylene containing ultra-violet stabilizer from a chlorofluorocarbon solvent, such as trichlorofluoromethane. Such solvents are known to react with atmospheric ozone, therefore, considerable effort has been expended to minimize the release of such solvents to the atmosphere, and alternative solvents have been sought.
One alternative solvent is pentane. However, when pentane is substituted for chlorofluorocarbon solvents when spinning polyethylene containing the ultra-violet stabilizer commonly used, another problem arises: namely, "dust" forms at the spinning nozzle, and dust deposits cover the apparatus and product. Chemical analysis of the "dust" has shown that it is primarily the ultra-violet light stabilizer.
An object of the invention is to provide a process for flash spinning polyethyene containing a ultra-violet stabilizer from pentane where the level of "dust" is at least as low as the dust level when the solvent is a chlorofluorocarbon.